Electrical engineering calculators
A growing collection of fast, accurate calculators for electricians, electronics hobbyists and EE students. Every tool runs instantly in your browser.
Basics & Ohm's law
Ω Ohm's Law
V, I, R, P from any two.
🔁 Watts / Volts / Amps
Convert between W, V and A for DC and AC.
➗ Voltage Divider
Output voltage from two resistors.
🔀 Current Divider
Split a current between two parallel resistors.
Resistors & capacitors
🎨 Resistor Color Code
Decode 4, 5 and 6-band through-hole resistors.
🔠 SMD Resistor Code
Decode 3-digit, 4-digit and EIA-96 SMD codes.
🔢 Capacitor Code
Decode 3-digit ceramic capacitor codes.
💡 LED Resistor
Find the correct series resistor for any LED.
🔌 Series / Parallel Resistors
Total resistance of any combination.
🔋 Series / Parallel Capacitors
Total capacitance of any combination.
Power, wiring & mains
📉 Voltage Drop
Voltage drop and % drop for a cable run.
🧵 Wire Size (AWG)
Minimum copper/aluminum conductor for a current.
⚙️ Three-Phase Power
kW, kVA, amps and power factor.
📐 Power Factor Correction
Capacitor kVAR needed to correct power factor.
🔌 Energy Cost
Running cost of any appliance per day, month, year.
🔁 kVA / kW / Amps
Convert between kVA, kW and current (1Ø/3Ø).
🔌 Transformer Sizing
Required transformer kVA and full-load current.
🌀 Motor Full-Load Current
FLA for single- and three-phase motors.
🧰 Conduit Fill
Minimum EMT/PVC/RMC size per NEC.
📊 Main Panel Capacity
Service capacity vs demand load and spare.
Home heating & EV
♨️ Sauna Heater Size
Recommended sauna heater power from room volume.
🔥 Room Heating Power
Watts needed to heat a room electrically.
🌡️ Underfloor Heating Cable
Floor heating power, cable length and spacing.
🚗 EV Charging Time
How long to charge an electric car battery.
🏠 Peak Power & Main Fuse
Peak kW to current, fuse size and tariff step.
❄️ Heat Pump Load
Electrical input power and breaker for a heat pump.
Solar, battery & EV
🔋 Battery Backup Runtime
How long a home battery powers your loads.
☀️ 48V Inverter Cable Size
DC cable cross-section for a battery/inverter run.
⚖️ EV Charger Load Sharing
Spare current and power per EV charger.
💰 EV Charging Cost
Cost to charge an EV and off-peak savings.
Electronics design
〰️ RC Filter Cutoff
Cutoff frequency and time constant of an RC filter.
⏱️ 555 Timer
Frequency, period and duty cycle (astable/monostable).
🔋 Battery Life
Runtime from capacity (mAh) and load current.
About these calculators
VoltCalc brings common electrical and electronics calculations into one fast, clean place. Whether you're sizing a cable, filling a conduit, picking a resistor for an LED or working out three-phase current, each tool shows the formula it uses so you can check the result. Everything runs in your browser — no sign-up, no waiting.